The present invention relates to semi-conductor devices and, more particularly, to a flexible lead structure for semi-conductor devices.
Semi-conductor wafers such as thin mono-crystalline silicon wafers used in semi-conductor devices are brittle and must be protected from the application of excessive forces during assembly and use of the semi-conductor device. A potential source of these forces is the lead bonded to the wafer. The lead will be subjected to various mechanical forces during assembly and operation of the device due to mechanical vibration and thermal expansion. Care must be taken to design the lead in such a manner that the transmission of these forces to the semi-conductor wafer is kept to a minimum.
A solution to this problem has been to include an expansion loop, such as a flexible C-shaped or S-shaped region, in the lead structure. Such leads are illustrated in U.S. Pat. No. 3,449,642, assigned to the assignee of the present invention.
While these devices have provided some degree of protection, they have been objectionable in at least one area. In order to maintain a low voltage drop and temperature rise, it is desirable to design the lead such that the cross-sectional area in the expansion loop is as least as great as the cross-sectional area of the remaining portions of the lead. In prior art devices, this has meant that the expansion loop must be comparatively thick to provide the necessary cross-sectional area. Additionally, since a single C-shaped or S-shaped bend was used, flexibility of the lead was largely limited to a single plane.